This application is based on application No. 2000-333926 filed in Japan on Oct. 31, 2000, the content of which is incorporated hereinto by reference.
This invention relates to a high current power supply apparatus primarily used to power a motor to drive a vehicle such as a hybrid or electric car.
A high current, high output power supply apparatus, used as a power source for a motor to drive an automobile, contains power modules. Power modules are a plurality of series connected batteries, and they are in turn connected in series to raise the output voltage of the power supply apparatus. The purpose of this is to increase the output of the driving motor. Extremely high currents flow in a power supply apparatus used for this type of application. For example, in a vehicle such as a hybrid car, when starting to move or accelerating, battery output must accelerate the car, and extremely high currents over 100A can flow. High currents also flow during short period, rapid charging.
In a high current power supply apparatus, forced cooling is required when battery temperature rises. In particular, in a power supply apparatus with many power modules inserted in vertical and horizontal columns and rows in a holder-case, it is important to uniformly cool each power module. This is because performance degradation will result for a battery which rises in temperature when battery cooling is non-uniform.
Systems which house a plurality of power modules in a holder-case and cool each power module more uniformly are cited, for example, in Japanese Patent Applications HEI 10-270095 (1998) and HEI 11-329518 (1999). As shown in the cross-sectional view of FIG. 1, the power supply apparatus of the former application cools internally housed power modules 21 by forcing air to flow from air intakes 23 which form the base of the holder-case 22 to exhaust outlets 24 which form the top of the holder-case 22. Cooling adjustment fins 25 are disposed inside the holder-case 22 to adjust the speed of air flowing over the surfaces of power modules 21.
In a holder-case 22 of this configuration, air flows more rapidly over the surfaces of power modules 21 disposed near the top than those near the bottom. The purpose of this is to avoid a temperature differential between power modules 21 at the top and bottom. If the flow rate of air passing over the surfaces of power modules 21 at the top and bottom is made the same, power modules 21 at the bottom will be cooled more efficiently than those at the top because air flowing over the surfaces of power modules 21 at the bottom has a lower temperature.
To make the flow rate of air over power modules 21 at the top faster than the flow rate over those at the bottom, the gap for air flow between the cooling adjustment fins 25 and the power modules 21 is gradually made narrower towards the top of the holder-case 22. This is because air flow becomes faster as the gap for air flow becomes narrower.
This type of power supply apparatus cools power modules near the bottom with cool air and power modules near the top with high flow rate air to establish a more uniformly cooled environment for power modules at both the top and bottom. However, it is extremely difficult to cool upper and lower power modules under very uniform conditions in this type of system. This is because the temperature of cooling air for power modules at the bottom is low, and the temperature of cooling air for power modules at the top becomes high. It is difficult to cool upper power modules with the same efficiency as lower power modules even by increasing the flow rate over power module surfaces when upper power module cooling air temperature has become high. For this reason power modules near the air intakes can be cooled efficiently, but power modules near the exhaust outlets are difficult to cool efficiently and this system has the drawback that a temperature differential develops over power modules housed in the holder-case. This has the deleterious effect that power modules, which are near exhaust outlets and very difficult to efficiently cool, become hot and easily degraded.
As shown in the cross-sectional view of FIG. 2, the power supply apparatus cited in the later patent application directs cooling air into the holder-case 27 from intermediate positions along the holder-case 27. Air directed into the holder-case 27 from intermediate positions supplies cool air to regions near the outlet and makes the inside temperature of the holder-case 27 uniform. This system can reduce the temperature differential across the holder-case 27, but the flow rate of air inside drops due to air entering from intermediate positions along the holder-case 27. To efficiently cool power modules 26, it is important to lower the temperature of the cooling air, but it is also important to increase the flow rate of air over the surfaces of the power modules 26. Even if cooling air temperature is lowered, the region of air immediately in contact with the surface of a power module will rise in temperature if flow rate slows. Since a power module 26 is cooled by the air in immediate contact with its surface, it cannot be efficiently cooled if the air temperature of this region becomes high.
The present invention was developed to correct these types of drawbacks seen in prior art power supply apparatuses. Thus, it is a primary object of the present invention to provide a power supply apparatus which can cool all of the plurality of power modules housed in a holder-case more uniformly and effectively prevent battery performance degradation caused by temperature differentials.
The above and further objects and features of the invention will more fully be apparent from the following detailed description with accompanying drawings.
The power supply apparatus of the present invention is provided with a plurality of power modules, a holder-case which houses the power modules arranged in rows in a parallel fashion and which cools the power modules by passing air through the inside of the case, and a fan which forcibly supplies air to the holder-case or intakes air through the holder-case. The holder-case is box shaped and has a first surface plate and a second surface plate disposed on opposite sides. A plurality of power modules are arranged side-by-side in a parallel fashion and in a single plane along the first surface plate and second surface plate. Further, walls are established between the plurality of power modules laterally arrayed in the holder-case. The walls extend from the first surface plate to the second surface plate to divide the interior into a plurality of rows of partitions, and one row of power modules are disposed in each partition row. In addition, the holder-case has flow inlets opened through the first surface plate to divide air flow and direct it into cooling ducts formed by the plurality of partition rows. Exhaust outlets are also opened through the second surface plate to expel air which has passed through the plurality of partition cooling ducts. The power supply apparatus uses the fan to divide and divert air flow through the first surface plate flow inlets into the plurality of partitions, passes air through the cooling ducts to cool the power modules, expels air which has performed its cooling function through second surface plate exhaust outlets, and thereby cools the power modules disposed inside the plurality of partition columns.
This configuration of power supply apparatus has the characteristic that all of the plurality of power modules housed in the holder-case can be more uniformly cooled, and battery performance degradation caused by temperature differentials can be effectively prevented. This is because the power supply apparatus of the present invention disposes a plurality of power modules side-by-side in a parallel fashion in a single plane, divides the interior of the holder-case with walls into a plurality of rows of partitions, disposes one row of power modules in each partition row, and causes air to divide and flow from the flow inlets of the first surface plate through the plurality of partitions and out the exhaust outlets of the second surface plate to cool the power modules disposed in the plurality of partition rows. Since one row of power modules is separately disposed in each partition row in this configuration of power supply apparatus, each power module is independently cooled by air passing through its cooling ducts without any influence from other power modules. Further, since cooling air passing through each partition cools only one row of power modules, that cooling air is fresh and not warmed by other power modules, and cooling can be extremely efficient. In this manner, a power supply apparatus which can cool each power module under ideal conditions can efficiently and uniformly cool all of the plurality of power modules.
The power supply apparatus of the present invention can be provided with an air inlet duct at the surface of the first surface plate. In this power supply apparatus, air flow can be directed from the air inlet duct, into the flow inlets, and through the partitions. Further, flow inlets opened through the first surface plate can be made smaller at the upstream end of the air inlet duct than at the downstream end of the air inlet duct. This configuration of power supply apparatus can uniformly supply cooling air to all partitions. In addition, the power supply apparatus may have a two tiered holder-case with the two tiers disposed in a parallel fashion in mutual opposition around the air inlet duct.
The power supply apparatus of the present invention can also be provided with an air outlet duct at the surface of the second surface plate. In this power supply apparatus, air passed through each partition and out each exhaust outlet is re-combined in the outlet duct and expelled from the system. Further, exhaust outlets opened through the second surface plate can be made larger at the upstream end of the outlet duct than at the downstream end of the outlet duct. This configuration of power supply apparatus can uniformly supply cooling air to all partitions. In addition, the power supply apparatus may have a two tiered holder-case with the two tiers disposed in a parallel fashion in mutual opposition around the outlet duct.
In the power supply apparatus of the present invention, the flow inlets and exhaust outlets can be made as slits extending in the lengthwise direction of the power modules.
In the power supply apparatus of the present invention, the power modules can be shaped as circular cylinders, the cross-sectional shape of the inside of the partitions housing the power modules can be polygonal with greater than or equal to eight sides, or the cross-sectional shape of the inside of the partitions can be circular to elliptical. In this power supply apparatus, cooling ducts are established between power module surfaces and partition inner walls, and air flow in the partitions flows along power module surfaces via these cooling ducts.
In the power supply apparatus of the present invention, cooling ducts can be made approximately the same width around the entire perimeter of each power module.
Further, in the power supply apparatus of the present invention, retaining projections extending from partition inner walls of the first surface plate and second surface plate can be formed by single piece construction to hold power modules in place. In this power supply apparatus, the ends of these retaining projections contact the surface of a power module and hold that power module in place inside the partition.
Still further, in the power supply apparatus of the present invention, the power modules can be shaped as circular columns, and these power modules can be disposed at partition centers.